KR101585277B1 - Two-component polyurethane adhesive for gluing fibrous molded parts - Google Patents

Abstract

The present invention relates to a process for the preparation of polyurethane compositions comprising 2 to 30% by weight of at least one polyester diol having a molecular weight of more than 1000 g / mol, 5 to 35% by weight of at least one 3 to 14 functional polyol, 5 to 35% And a crosslinking component made from a polyisocyanate having an NCO / OH ratio of from 0.9: 1 to 1.5: 1 together with a polyol component containing from 2 to 65% by weight of further additives or auxiliaries so that the sum is 100% The adhesive relates to a two-component polyurethane adhesive having a T _g of greater than 50 ° C.

Description

[0001] TWO-COMPONENT POLYURETHANE ADHESIVE FOR GLUE FIBROUS MOLDED PARTS [0002]

The present invention relates to a polyurethane-based two-component adhesive exhibiting high adhesive strength. Further, the present adhesive can also bond a substrate having a roughened surface and can bond a gap or a gap with a strong adhesive bond.

WO 2004/029121 describes a two-component polyurethane adhesive consisting of a diol and a triol-based polyol and crosslinked by a polyisocyanate. In addition, pigments such as highly disperse silica, fillers and molecular sieves must be present. In the above invention, an organic acid having a pKa value of 2.8 to 4.5 is present as an essential component. The addition of a high-functionality polyol to increase the network density is not described. Moreover, it is known that carboxylic acid during cross-linking of isocyanate groups can increase bubble formation.

WO 2002/066527 contains less than 98% of oleochemical polyols, 1 to 7.5% of low molecular weight diols having an OH value of 400 to 2000, and 1 to 7.5% of 3 to 5 functional polyols , A two-component polyurethane adhesive for a derivative wood containing further auxiliaries and resins, describes an adhesive which can be crosslinked by polyisocyanate.

EP 0794977 describes a two-component polyurethane adhesive consisting of a polyol, a highly disperse silica, a filler and a molecular sieve and crosslinked by a polyisocyanate. Diols and triols are used as polyols.

It is described that the adhesive is used for bonding wood and metal; There is no description to use for bonding plastic substrates which should exhibit high mechanical stability even when a heat load is applied.

Similarly, it is known to bond a glass fiber reinforced plastic substrate. Since such substrates exhibit high mechanical stability, corresponding adhesives are likewise required to withstand the corresponding strengths. Examples of such bonding operations include bonding fiber reinforced parts for wings or other aircraft fittings, bonding fiber reinforced parts in the shipbuilding industry, or bonding fiber reinforced parts in the manufacture of blades for wind power systems . This has a high mechanical requirement for the adhesive component. It has to withstand high tensile force, and the load applied by constant vibration is high, causing material fatigue. In addition, the environmental impact is severe, and the characteristics must be stable at various humidity levels, and at the same time, stability must be ensured even at greatly varying temperatures. It is known here to bond these components with a two-component epoxy adhesive. Although this exhibits sufficient strength, it has various processing disadvantages. For example, a high curing temperature is essential to achieve sufficient strength. In addition, the substrate surface must be specially prepared for adhesion.

Conventional adhesives have the disadvantage that adhesive bonding has insufficient mechanical stability under various climatic and temperature conditions. Moreover, these are not suitable for bonding a large area because the working time before bonding the substrates is not long enough. Further, the adhesive is not suitable for frictionally connecting the irregularities in the bonded substrate.

Accordingly, an object of the present invention is to provide an adhesive which can adhere plastic substrates to each other without pretreatment, has an open time of a long time, and stably adheres to uneven surfaces. The crosslinked adhesive layer should be insensitive to moisture and varying ambient temperature, and should remain stable in terms of mechanical properties.

It is an object of the present invention to provide a composition comprising 2 to 30% by weight of at least one polyester diol having a molecular weight of greater than 1000 g / mol, 5 to 35% by weight of at least one 3 to 14 functional polyol, 5 to 35% by weight of hydrophobic polyol % Of an isocyanate component prepared from a polyisocyanate component having an NCO / OH ratio of 0.9: 1 to 1.5: 1 together with a polyol component containing 2 to 65% by weight of further additives or auxiliary substances so that the total is 100% the crosslinked adhesive is accomplished by a two-component polyurethane adhesive showing a T _g of greater than 50 ℃.

The present invention also provides the use of such a two-component polyurethane adhesive for bonding fiber-reinforced plastics, in particular fiber-reinforced components in the manufacture of blades for wind power systems.

Known molds made of high strength fiber composites are suitable as substrates. These may be composed of, for example, glass fibers, carbon fibers or aramid fibers embedded in a plastic matrix. These fibers may be introduced in the form of a mat, fabric, nonwoven fabric or roving. The plastic matrix may be comprised of polyester or epoxy and reacted by a suitable curing agent and / or crosslinking agent to form a thermosetting polymer. Such fiber-reinforced substrates are known to those skilled in the art. For example, in aircraft manufacturing, shipbuilding, or other parts where high mechanical loads are applied. One specific application field for such an adhesive substrate is a blade for a wind turbine rotor. Further, a manufacturing method for such a molded part is known.

Such blades are made, for example, in the mold cavity and crosslinked. The molds are often fabricated as an accordion. The mold facing side is usually a smooth and readily usable surface, while the other side may require additional processing and typically requires additional processing. The blades are continuously produced to bond two or more of these substrates together. The side to be bonded is usually the side away from the mold. The surface should have a structure in which a base material portion to be adhered is almost fitted. The surface provided for bonding may be rough and may be non-uniform per se. There is no need to sand or mill to form the correct symmetrical shape with the other side to be bonded. When using the adhesive according to the present invention, pretreatment of the surface to be adhered is not required. It is sufficient to apply the adhesive to a dust and grease free surface, so that the use of a primer is not required.

Once the part is fabricated in a mold, covering the surface on the outside of the mold for crosslinking with the thermosetting protective fabric is known as one of the working methods. Which can be completely detached prior to subsequent bonding operations to provide a suitable surface. On the other hand, it is also possible to roughly make such a surface to fit the corresponding surface. The adhesive according to the invention can be applied on the surface of the substrate produced in this way and can have no base particles and dust.

The two-component polyurethane adhesive according to the present invention has fluidity but may also exhibit also thixotropic properties. It consists of a polyol component and an isocyanate component. These are mixed just before application. The polyol component should contain various polyfunctional polyols. This is to ensure sufficient cross-linking for mechanically stable bond bonding even when exposed to a heat load. In addition, sufficient hydrophobicity of the adhesive should be obtained by selection of various polyols.

The hydrophobic polyol is a component of the polyol component. Suitable polyols include, for example, liquid polyhydroxy compounds having an average of from 2 to 4 hydroxyl groups per molecule. For example, polycarbonate polyols are suitable as hydrophobic polyols. These are carbonate esters obtained by reacting carbonic acid derivatives, for example, phosgene or diphenyl carbonate, with diols. For example, low molecular weight aliphatic diols are suitable here. For example, an OH-functional polybutadiene available under the trade designation "Poly-bd" can also be used as the hydrophobic polyol for the composition according to the invention.

The molecular weight of these polyols is usually in the range of 300 to 5000 g / mol, preferably 500 to 3000 g / mol (number average molecular weight M _N , as measured by GPC).

On the other hand, a hydrophobic polyol derived from a fat may be used. Means a reaction product of a mono-, di- or polyfunctional alcohol with an epoxidized fatty component, or a reaction product of an epoxidized fatty component with at least partially substituted It is a glycerol ester of long chain fatty acids. Such a polyester polyol can be produced, for example, by completing the ring opening of the epoxidized triglyceride carried out while maintaining the ester bond. Examples of alcohols that can be used for ring opening of the epoxidized triglyceride include alcohols such as methanol, ethanol, propanol, isopropanol, butanol, hexanol, 2-ethylhexanol, fatty acid alcohols having 6 to 22 carbon atoms, cyclohexanol, -Ethanol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, trimethylolpropane, glycerol, trimethylolethane, pentaerythritol, sorbitol and Ether group-containing hydroxyl compounds such as alkyl glycols or oligomer glycols and oligomer glycerol.

A further group of oil-derived polyols are the ring opening and transesterification products of epoxidized fatty acid esters of lower alcohols, such as the epoxidized fatty acid methyl, ethyl, propyl or butyl esters. Here, a reaction product of a ring-opening or ester exchange reaction using an alcohol having a functionality of 2 to 4, in particular, ethylene glycol, propylene glycol, oligomer ethylene glycol, oligomer propylene glycol, glycerol, trimethylol propane or pentaerythritol is preferable Do.

For the purposes of the present invention it is also possible to use ei- or pluripoproteins such as, for example, reaction products in which ethylene oxide or propylene oxide is added to glycerol together with triglycerides such as palm oil, peanut oil, rape oil, cottonseed oil, soybean oil, sunflower oil, A fat-derived polyol that can be obtained by an ester exchange reaction of a soluble alcohol may be used.

After completion of the ring opening of the epoxidized triglyceride of the fat-and-oil mixture containing at least part of the olefinically unsaturated fatty acid having at least one alcohol having 1 to 12 carbon atoms, partial ester exchange of the triglyceride derivative results in 1 to 12 It is particularly preferable to use castor oil and dimer diol as the polyol derived from hydrophobic retention together with the polyester polyol produced by obtaining the alkyl ester polyol having carbon atoms. These fat-derived polyols may have a hydroxyl value of from 50 to 400, preferably from 100 to 300, wherein the molecular weight is from about 500 g / mol to less than 1500 g / mol.

The functionality of the hydrophobic polyol should on average be 2.2 to 4, in particular more than 2.4. Mixtures may be used and the individual components may contain OH groups. Such hydrophobic polyols are commercially available.

The amount of the hydrophobic polyol should be 5 to 50% by weight, especially 35% by weight or less. Also, the amount may vary depending on the strength of the hydrophobicity of the polyol. With respect to the mixture of all the polyols, the object is to obtain a hydrophobic mixture.

An additional essential component is a more highly functionalized polyol having 3 to 14 OH groups, especially 4 to 9 OH groups. These polyols improve the cohesion by increasing the cross-linking density of the polymer. These may include a mixture of polyols.

Examples of such polyols include sugar alcohols containing an appropriate number of OH groups, especially tetritol, pentitol or hexitol, or disaccharides. Corresponding sugars may be used, but especially hydrogenated sugar alcohols may be used. For example, there may be mentioned, for example, sorbitol, inositol, mannitol, traitol, erythritol, adonitol, arabitol, ribitol, xylitol, dulcitol, ribose, xylose, ricosource, glucose, galactose, mannose, But are not limited to, roots, gulose, idose, talos, fructose, sorbose, psicose, tegatose, deoxyribose, glucosamine, galactosamine, rhamnose, digethoxose, sucrose, Roots, maltose, cellobiose, melibiose, genentobiose, and lutinose. Corresponding ethoxylated and propoxylated products having alkylene oxide units of up to 15 can be used.

A polyol having at least one tertiary amino group and having 4, 5 or 6 OH groups is also suitable. Examples thereof are propoxylation or ethoxylation products of C ₃ to C ₆ diamines or triamines. Ethoxylated and propoxylated products of ethylenediamine are particularly suitable.

The molecular weight of this more highly functionalized polyol may be from 120 to 3000 g / mol, especially from 250 to 2000 g / mol.

Polyether polyols can be used. Examples of these are the reaction products of 3 to 6 functional alcohols which can be produced by reaction with ethylene oxide or propylene oxide, for example polypropylene glycol. A further group of suitable polyether polyols are, for example, polytetramethylene glycols which can be produced by acid polymerization of tetrahydrofuran. The molecular weight of these polyether polyols is usually in the range of 200 to 6000 g / mol, preferably 400 to 3000 g / mol.

Mixtures of different 3 to 14 functional polyols may be used, and in particular polyether polyols and sugar polyols are suitable for use alone or as mixtures.

The more highly functionalized polyols typically have OH groups. Alternatively, in another embodiment, it is also possible that at least some of the -SH groups -NHR groups are present as reactive functional groups.

Due to the number of reactive OH or NH groups, the more highly functionalized polyols have a relatively high polarity. It can be partially miscible with water. The amount of the highly functionalized polyol and the hydrophobic polyol should be adjusted so that the mixture exhibits the hydrophobic character. Otherwise, it is difficult to obtain a bubble-free adhesive, and furthermore, the mechanical stability of the adhesive bond is not secured at high atmospheric humidity.

A simple test to compare the minority properties is to mix a mixture of polyol and 1% water and mix until uniform at 25 ° C. Addition of crude MDI in a positive ratio of 1: 1 and mixing gives a substantially hydrophobic mixture cross-linking resulting in a substantially bubble-free polymer, whereas a foam is obtained if the hydrophobic action is insufficient . A volume increase of about 20% should no longer be appropriate anymore, and should occur without bubbles or just being isolated.

A further essential component of the two-component polyurethane adhesive according to the invention is a carboxylic acid-based polyester diol having a diol. Suitable polyester diols have a molecular weight of about 1000 to about 15,000 g / mol. For example, a polyester polyol obtained by reacting a low molecular weight alcohol with a lactone can be used. Examples of alcohols include ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerol, trimethylol propane, 1,4-hydroxymethylcyclohexane, Triethylene glycol, tetraethylene glycol, dipropylene glycol, dibutylene glycol and polybutylene glycol having not more than 10 repeating units, polyethylene glycol, and polypropylene glycol.

Additional suitable polyester polyols may be produced by polycondensation. Bifunctional and / or small amounts of trifunctional alcohols can be condensed in the absence of dicarboxylic acids and / or tricarboxylic acids or reactive derivatives thereof to form polyester polyols. An aromatic or aliphatic carboxylic acid can be used. Suitable dicarboxylic acids are, for example, adipic acid or succinic acid and their higher homologues of up to 16 carbon atoms and also include unsaturated dicarboxylic acids such as maleic or fumaric acid, aromatic dicarboxylic acids, especially phthalic acid, Or terephthalic acid. For example, citric acid or trimellitic acid is suitable as the tricarboxylic acid. The stated acids may be used alone or as a mixture of two or more. Particularly preferred are polyester polyols made from aliphatic dicarboxylic acids using aliphatic linear, branched or alicyclic diols, such as polyester polyols prepared from the above-mentioned diols. Particularly suitable alcohols are hexanediol, ethylene glycol, diethylene glycol or neopentyl glycol or mixtures thereof. Particularly suitable are acids of 4 to 12 carbon atoms, for example succinic acid, azelaic acid, suberic acid, sebacic acid or adipic acid or mixtures thereof.

The polyester diol should have a low melting point or be liquid at room temperature. The molecular weight may be preferably from 1500 to 8000 g / mol. The polyol may have a functionality of about 1.8 to 2.2 and is typically in the diol form. The polyester diol is advantageous because it promotes the miscibility of the hydrophobic and polar polyol.

The polyol component comprises from 2 to 30% by weight of at least one polyester polyol, from 5 to 50% by weight of a hydrophobic polyol and from 5 to 35% by weight of a polyfunctional polyol having from 3 to 14 OH groups and from 2 to 65% . Preferred embodiments should contain additives with 5 to 20 wt% polyester polyol, 10 to 30 wt% hydrophobic polyol, 10 to 30 wt% polyfunctional polyol. Here, the total percentage of the polyol component should be 100%.

 The various polyol components affect the essential properties of the crosslinked additive. If the amount of the polyol having 3 to 14 OH groups is too low, sufficient aggregation of the adhesive can not be obtained. The amount of these polyols can affect the cross-linking density of the adhesive, furthermore affecting the glass transition temperature. If the amount of the hydrophobic polyol is not sufficient, mechanical defects such as gas bubbles may be caused upon bonding. In addition, open time required for machining may be adversely affected.

The multifunctional isocyanate is suitable as the polyisocyanate in the isocyanate component. Suitable isocyanates preferably contain from 2 to 5, preferably up to 4, NCO groups on average. Suitable isocyanates include 1,5-naphthylene diisocyanate, 2,4- or 4,4'-diphenylmethane diisocyanate (MDI), hydrogenated MDI (H12MDI), xylylene diisocyanate (XDI), m- and p- Tetramethyl xylylene diisocyanate (TMXDI), 4,4'-diphenyldimethylmethane diisocyanate, di- and tetraalkyldiphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene di Isocyanate, 1,4-phenylene diisocyanate, isomer of tolylene diisocyanate (TDI), 1-methyl-2,4-diisocyanatocyclohexane, 1,12-diisocyanatododecane, 1,6- 2,2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclo Hexane (IPDI), tetramethoxybutane, 1,4-diisocyanate, butane 1,4-diisocyanate, hexane 1,6-diisocyanate (HDI), dimer fatty acid diisocyanate, dicyclohexyl methane diisocyanate, a sayikeu hexane, 1,4-diisocyanate, ethylene diisocyanate, phthalic acid or bis-ester is isocyanatoethyl.

It is also possible to use reaction products of low molecular weight prepolymers having a large number of isocyanate groups, that is to say oligomers such as low molecular weight diols of MDI or TDI, such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol or triethylene glycol . These oligomers are obtained in the case of an excess of monomeric polyisocyanates in the presence of a diol. Wherein the molecular weight of the diol is typically less than 1500 g / mol. The monomers may be optionally removed from the reaction product by distillation. Also suitable are isocyanates, for example buret compounds and isocyanurates of HDI or IPDI, and carbodiimide-liquefied diphenylmethane diisocyanate or crude MDI.

Aliphatic and alicyclic polyisocyanates can be used and the reactivity thereof can be increased by a high temperature or by a catalyst. On the other hand, aromatic polyisocyanates are preferred, and there are oligomerized NCO-terminal adducts prepared from the above-specified aromatic isocyanates and low molecular weight diols. Preferably the polyisocyanate should be fluid at room temperature.

The two-component polyurethane adhesive according to the present invention may further comprise an auxiliary material, and is preferably wholly or partly mixed with the polyol component. This can be achieved by modifying the properties of the adhesive in the desired direction, such as viscosity, wetting behavior, stability, reaction rate, bubble formation, shelf life or adhesion, . Examples of auxiliary materials include fillers, leveling agents, degassing agents, tackifiers, catalysts, antioxidants, dyes, drying agents, resins, plasticizers and wetting agents.

For example, a catalyst may be used when using an aliphatic isocyanate. The catalysts used are conventional organometallic compounds known in the polyurethane art, for example iron compounds or especially tin compounds. Examples thereof include iron 1,3-dicarbonyl compounds such as iron (III) acetylacetonate, and especially organotin compounds of 2- or 4-valent tin, especially Sn (II) carboxylate or dialkyl -Sn (IV) dicarboxylate or the corresponding dialkoxylates such as dibutyltin dilaurate, dibutyltin diacetate, dioctyltin diacetate, dibutyltin maleate, tin (II) octoate have. In particular, tertiary amines or amines can optionally be used as catalysts in combination with the tin compounds specified above. Amines which may be considered here are both acyclic and especially cyclic compounds. Examples thereof include tetramethylbutane diamine, bis (dimethylaminoethanol) ether, 1,4-diazabicyclooctane (DABCO), 1,8-diazabicyclo- (5.4.0) undecene, Dimorpholonodiethyl ether, dimethylpiperazine, or mixtures of the above-specified amines. In another preferred embodiment of the two-component polyurethane adhesive according to the present invention, it is processed without a catalyst.

In addition, the adhesive according to the invention may optionally contain further stabilizers. "Stabilizer" should be understood to mean antioxidants, UV stabilizers or hydrolytic stabilizers for the purposes of the present invention. Examples thereof are customary commercially available sterically hindered phenols and / or thioethers and / or substituted benzotriazoles and / or amines of the type "HALS" (Hindered Amine Light Stabilizer).

In addition, resins may optionally be present. Which may include natural resins or synthetic resins. Examples thereof include shellac, rosin, tall oil resin, gum resin or wood resin, hydrocarbon, terpene, coumarone / indene, furan, alkyd, glycerol ester, urea, melamine, polyamide resin, especially aldehyde, ketone or phenolic There is resin. The resin typically has a low melting point and is advantageous among others in that the miscibility of the components is improved. In one particular embodiment, a resin containing an OH group, particularly a plurality of OH groups, is used. It can also react with isocyanates. In a preferred embodiment, the amount thereof may be from 5 to 30% by weight.

Moreover, the composition according to the present invention may further contain additives and additives known per se, for example plasticizers, tackifiers, coloring pastes or pigments. Suitable fillers are inorganic compounds that are not reactive with isocyanates. Examples of suitable fillers and pigments are natural, ground chalk, precipitated chalk, barite, talc, mica, carbon black, titanium dioxide, iron oxide, aluminum oxide, zinc oxide, zinc sulphate or silicon dioxide. Hygroscopic powder, for example zeolite, may be present as a filler. The filler should be present in an undifferentiated form, for example of size 1-200 μm, in particular 50 μm or smaller, but may also be a nanoscale pigment. The amount of fillers and pigments should be from 0 to 60% by weight, in particular from 5 to 40% by weight. The amount of filler affects the hardness of the crosslinked adhesive. It is also possible to influence the viscosity by the amount and the selection of the filler.

The additive is selected so that it does not participate in any reaction with the isocyanate or the secondary reaction, or at least does not participate throughout the cross-linking reaction. In particular, additives which promote the formation of bubbles in the adhesive, for example, carboxylic acids, should not be added. Further, the adhesive according to the present invention should preferably not contain an organic solvent which is volatile at a temperature of 120 DEG C or lower. In particular, plasticizers should also not be present.

The ratio of isocyanate groups present in the isocyanate component to the OH groups present in the polyol is typically equivalent and it is convenient to provide a slight excess of isocyanate groups for the water present on the surface. The NCO / OH ratio should be from 0.90: 1 to 1.5: 1, especially from 1.0: 1 to 1.3: 1.

The two-component polyurethane adhesive according to the present invention is prepared by first preparing a polyol component. For this reason, after mixing the liquid polyol, all the solid content in the mixture should be dissolved. It can also be assisted by heating. The auxiliary materials are then mixed and dispersed. At this time, the water content should be kept low, for example, the molecular sieve can be used to reduce the amount of water. Some inert auxiliary materials may be blended into the isocyanate component. Keep the two components until use. In use, these two components are mixed together in a manner known per se, and the mixture is applied to a substrate to be adhered.

The adhesive according to the invention should be in the form of a liquid or paste at the application temperature, for example 10 to 40 占 폚. It must be able to be applied as a film or bead, and should not flow on the substrate during application. The adhesive mixture according to the invention is particularly thixotropic.

It is often necessary to adhere a large area and an open time is required for a long time in order to precisely align the substrate portion to be adhered. According to the invention, an open time is achieved in excess of 30 minutes, in particular over 60 minutes. Open time is defined as the period of time in which the concentration of the adhesive is maintained for proper processing before the concentration of the adhesive is changed to such an extent that the application of the coating liquid onto the substrate and excellent adhesion is no longer achieved due to the initiation of the reaction it means. The change in the adhesive composition may be due to the desired crosslinking reaction, but the secondary reaction may have a negative effect on the pot life.

The open time for a long time can be influenced by the amount of hydrophobic alcohol. If the amount of the hydrophobic polyol is too small, a sufficient open time can not be obtained. The adhesive is rapidly crosslinked and bubble formation is observed. Catalysts can also affect reaction rate and open time. The moisture content of the polyol component should be less than 2% by weight, especially less than 1% by weight, preferably less than 0.5% by weight.

By selecting these components, it is achieved that the adhesive has a glass transition temperature (T _g ) of from 50 to 130 ° C, in particular from 60 to 110 ° C (in DSC measurement, DIN 11357). High T _g is essential to obtain the required mechanical stability. The selection of hydrophobic polyols and polyfunctional polyols in accordance with the present invention provides high mechanical stability of the crosslinked adhesive. Suitable adhesives according to the invention produce a hydrophobic network after crosslinking. In this respect, insufficient amounts of hydrophobic alcohols lead to uneven T _g upon exposure to water. According to the present invention, the glass transition temperature should deviate from the initial value by 20% or less after immersing the test piece in water (1000 h, distilled water, 25 캜).

In a further embodiment, the adhesive may have a glass transition temperature of at least 2. Here, the second glass transition temperature should be lower than the first glass transition temperature. For example, the second T _g may be a temperature in the range of -50 ° C to + 70 ° C, especially -10 ° C to + 40 ° C.

The structural stability of the adhesive bond can be measured, for example, by the modulus of elasticity. The modulus of elasticity should be greater than 1000 MPa (similar to DIN EN ISO 527) at a measurement temperature of -10 ° C to +70 ° C.

The two-component polyurethane adhesive according to the invention can be used particularly for bonding fiber composites. Here, the substrate is manufactured as a cast part. The surface to be bonded must be free of contaminants and can be used directly in the manufacturing process. It is customary to temporarily protect these surfaces with protective woven fabrics and then remove them before further processing. The adhesive according to the invention is applied on this surface in the form of a layer, bead or spot. The layer thickness may be less than 2 cm. Additional substrates are applied, aligned, optionally pressed and secured. In this process, the flowable adhesive is uniformly distributed over the surface of the substrate. Because of the increase in the layer thickness, the irregularities of the surface to be adhered are evened by the adhesive, and the substrate can make extensive contact.

Thereafter, the adhesive bond is cured. Curing can proceed at room temperature, and crosslinking can optionally be promoted by raising the temperature to 90 ° C or less. After crosslinking, the adhesives according to the invention exhibit high mechanical strength. The adhesive bond exhibits a shear strength of greater than 15 MPa as measured by DIN EN 1465.

To improve adhesive bonding, it may be advantageous to thermally process the bonded substrate when the adhesive is crosslinked. Adhesive bonding should be adjusted to an elevated temperature of 40 to 100 DEG C for 30 minutes to 24 hours. Without being bound by a particular theory, it is assumed that internal positioning of the cross-linking sites and crystalline regions occurs, resulting in stable service characteristics. The use of the two-component polyurethane adhesive according to the present invention reduces the crosslinking time or the required temperature. As a result, the load on which the composite is exposed in the manufacturing process is also reduced. And may or may not limit heat treatment.

Once cured, the adhesive according to the invention is mechanically stable even at elevated temperatures. In this way, gaps, gaps or holes of 2 mm or less can be filled with an adhesive, resulting in strong adhesive bonding. Adhesive bonding is also stable when exposed to varying loads occurring when the blade is used as a rotor. Vibration, changes in temperature or increased water exposure caused by various environmental influences do not weaken adhesive bonding.

The following examples illustrate the invention.

Polyester polyol A: molecular weight = 2000; Prepared by reacting adipic acid with butanediol or hexanediol; f = 2

Hydrophilic polyol: castor oil

Polyol B1: molecular weight = 700; Polyether polyols; f = 3

Polyol B2: N, N, N ', N "-tetra (2-hydroxypropyl) ethylenediamine; f = 4

The components of the polyol component (amounts are by weight) are mixed at room temperature. The adhesive is prepared by mixing the polyol component with isocyanate, and within 30 minutes a suitable test piece is prepared and cured.

Curing: 48 hours at 40 ° C

The polyol component layer is mixed with 1% water, then mixed with an equal amount of MDI and cured at room temperature as an object having a diameter of about 1 cm and a diameter of 5 cm. A solid containing little bubbles is obtained.

Example 3 (comparative)

The composition according to Example 1 was prepared by replacing castor oil (hydrophobic polyol) with a corresponding amount of polyethylene glycol (molecular weight about 1000, trifunctional). The amount of zeolite was lowered to 1.

Upon curing, the thick adhesive beads showed bubbles and as a result were found to be mechanically unstable. Likewise, a mixture of polyol components with 1% water and an equivalent amount of isocyanate cured by violent bubble formation.

Example 4 (comparative)

A mixture according to Example 2 is prepared. Polyol B is replaced with polyether diol (molecular weight 800).

The adhesive is cured. On the other hand, the glass transition temperature was found to be less than 40 ° C. The mechanical properties (e.g., modulus of elasticity) of the adhesive were inadequate.

Claims (14)

a) 2 to 30% by weight of at least one polyester diol having a molecular weight in excess of 1000 g / mol,
b) from 5 to 35% by weight of at least one 3 to 14 functional polyol selected from the group consisting of sugar alcohols, polyether polyols and polyols containing amino groups,
c) from 5 to 35% by weight of at least one hydrophobic polyol selected from the group consisting of polycarbonate, polybutadiene and oleochemical polyols,
d) with a polyol component containing from 2 to 65% by weight of further additives or auxiliary substances so that the total is 100%
Wherein the crosslinked adhesive comprises a isocyanate component made from a polyisocyanate having an NCO / OH equivalent ratio of from 0.9: 1 to 1.5: 1, wherein the crosslinked adhesive exhibits a Tg of _greater than 50 < 0 > C. The method according to claim 1,
The hydrophobic polyol c) has a functionality of 2.3 to 4. 3. The method according to claim 1 or 2,
Wherein the polyester diol is synthesized from at least one diol and an aliphatic dicarboxylic acid selected from the group consisting of low molecular weight linear aliphatic diols, alicyclic diols and branched diols, and having a molecular weight of 15000 g / mol or less, . 3. The method according to claim 1 or 2,
Polyol b) is a polyol having 3 to 9 OH groups, and is selected from polyols containing sugar alcohols, polyether polyols or amino groups. 3. The method according to claim 1 or 2,
A two-component polyurethane adhesive in which the resin is present as an additive. 3. The method according to claim 1 or 2,
A two-component polyurethane adhesive in which aromatic polyisocyanates are used. 3. The method according to claim 1 or 2,
A two-component polyurethane adhesive in which the adhesive does not contain a solvent and does not contain a plasticizer. 3. The method according to claim 1 or 2,
Wherein the crosslinked adhesive exhibits a T _g of greater than 60 캜 but less than 130 캜. 9. The method of claim 8,
A two-component polyurethane adhesive in which the crosslinked adhesive exhibits hydrophobicity and the glass transition temperature T _g after immersion in water deviates from the initial value by less than 20%. 3. The method according to claim 1 or 2,
A two-component polyurethane adhesive wherein the crosslinked adhesive has two glass transition temperatures (T _g ), wherein the second T _g is lower than the first T _g of the two T _g . 3. The method according to claim 1 or 2,
Wherein the adhesive exhibits a modulus of elasticity greater than 1000 MPa at a temperature of from -10 DEG C to 70 DEG C after cross-linking. The two-component polyurethane adhesive according to any one of claims 1 to 3, which is used for bonding metal, plastic or foam substrate or fiber composite. delete delete